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Photonic Band Gap (PBG) materials are a new class of material that are the photonic equivalent of semiconductors. The PBG is essentially an energy range or frequency interval where a material can neither absorb nor allow the propagation of light. PBG materials are made up of alternating regions of high dielectric contrast . PBG materials can be modified- usually via doping-to allow the flow of certain forbidden energies and to guide the flow of light. There are many applications for PBG materials ranging from optical telecommunications, to quantum computers.
AFM can be used to zoom into PBG structures and this is demonstrated below. Also NSOM can be used to view the light distribution in such materials; this combined with AFM makes for powerful correlation analysis and characterisation.
Below is shown an AFM line profile of a row of particles in the PBG device:
The topography of PBG materials can be correlated with light concentration as demonstrated below.
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In this PBG material gaps develop between Domains.
On the left is shown an AFM(topographic) image of such a gap with a depth of 3 microns. On the right is shown an NSOM image, obtained in collection mode of the same region of the PBG material.
The sample is illuminated from below using a UV lamp- Nanonics' open architecture allows for such a setup. |
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Below is shown a collage of the AFM image and the NSOM image thus combining topographical information with light distribution. The image clearly shows that the light is concentrated in the gaps and "clings" preferentially to the walls.
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A collage of the AFM and NSOM images of the PBG material.
Light is seen to be concentrated in the gaps.
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Below we see an image obtained in collection mode NSOM. The image shows green light in a domain (bright triangular region to the left) that is propagating in a gap that has developed between two dark domains- seen emanating from the triangular region.
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NSOM (collection mode) of guided light in a PBG material |
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